This disclosure is related to the field of utility (e.g., sewage) access shafts, more commonly known as “manholes.” More particularly, the disclosure relates to methods and apparatus for drilling ports in a side wall of a manhole to enable sealing engagement of an additional utility conduit with a manhole.
Utility access shafts or “manholes” known in the art include cast concrete, substantially cylindrical conduits. The conduit is typically cast so as to be closed at one longitudinal end, and is open at the other longitudinal end. The conduit may be disposed in a hole from which soil has been removed for the purpose of placement of the conduit. The open end of the conduit may be disposed approximately at ground level and may be covered by a removable grating, plate or cover. The wall of the conduit may have cast therein one or more substantially circular openings into which utility lines, such as sewage pipes are sealingly connected. Sealing connection may include an elastomer sleeve which may be retained in one of the circular openings using an internally expanding retainer band.
It is known in the art that existing access shafts may require modification to connect additional utility conduits thereto after the shaft has been initially installed in the ground. Modification may require the creation of additional holes in the side wall of the access shaft for sealed connection of one or more additional utility conduits. It is known in the art to create such additional holes by using hand tools and a hammer. Such methods have more recently been banned by regulatory agencies because of the risk of brittle fracture of parts of the access shaft distal from the hammered-out hole, with associated risk of leakage or access shaft failure.
It is also known in the art to use a drill to create a substantially circular pattern of small holes where the one or more additional holes are to be located. After the full circular pattern is drilled, the remaining concrete inside the pattern may be removed such as by hammering. The hole thus created requires extensive finishing work to create a smooth, substantially round surface for sealing engagement of a utility conduit therein.
There exists a need for more efficient methods and apparatus for creating holes in access shafts for sealed connection of utility conduits or pipes thereto.